Iron plays an important role in biology, combining with molecular oxygen in hemoglobin and myoglobin, typical proteins used to transport oxygen in vertebrates. Iron is also a metal found in many important redox enzymes responsible for cellular respiration, oxidation and reduction in plants and animals. The average man has 4 grams of iron in the body, and a woman about 3.5 grams.

Iron is an element necessary for life for almost all living organisms – microbes, plants and animals, including man. Despite significant distribution on Earth, iron belongs to microelements – it is found in small amounts in the composition of organisms. It is found in prosthetic groups of many important proteins (metalloproteins): hemoglobin, myoglobin, including active centers of numerous enzymes such as: catalase, peroxidases and cytochromes.

Iron in the human body
Iron is found in the human body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin and plasma.
The need for iron in man is variable and depends on the age, sex and condition of the body. In adults, it ranges from 1 mg / day in men to 2 mg in women, with the proviso that during pregnancy and lactation it should be about 3 mg / day.

The differences in the absorption of iron from food are very large depending on the diet, from 1-2% for a cereal-only diet, up to 25% for a meat-based diet. For an average, mixed diet, the absorption of iron is about 10%, which means the need to consume about 10 times more iron than the body needs. Sometimes consumption does not meet the body’s need for this element, which after some time leads to its deficiency and the symptoms associated with it (iron deficiency anemia). Sometimes, despite the body’s existing regulatory mechanisms, iron overload can occur. The most important condition associated with excess iron in the body is hemochromatosis. Large amounts of iron (II) salts are toxic. Iron (III-VI) compounds are harmless because they are not absorbed.

Normal serum iron levels:
average value
• men 21.8 μmol / l, 120 μg / dl
• women 18.5 μmol / l, 100 μg / dl
extreme value
• men 17.7–35.9 μmol / l, 90–200 μg / dl
• women 11.1–30.1 μmol / l, 60–170 μg / dl

Iron is absorbed in the duodenum and small intestine in the form of Fe2 +. After absorption, it is bound by apoferritin in the gastrointestinal mucosa. Ferritin is formed and the iron is in oxidation state III. In the blood it is transported by transferrin. It is also stored in the liver in the form of ferritin.
Deficiency occurs in states of increased demand, absorption disorders or increased iron loss. In this case, anemia may occur. Supplementation with iron preparations should be introduced. It should be used, among others in people after surgery with high blood loss, in people with bleeding from the gastrointestinal tract, from the genital tract, pregnant and lactating women, with abundant menstruation, in premature babies, in children after a serological conflict, in people with iron absorption disorders.

Some studies indicate that iron administration may reduce the intensity of symptoms in children with ADHD who have deficiencies of this element. However, the role of iron supplementation in this disease is not confirmed and requires further research.
Sources of iron: meat (including fish meat), liver, egg yolk, cottage cheese, nuts, milk, legumes, broccoli, shrimp. Contrary to popular belief, spinach contains moderate amounts of iron and is in poorly absorbed form by humans.